linux-kernel - Re: [PATCH] ntb: use 64-bit arithmetic for the MSI doorbell mask

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Message-ID: <a8b2695d-7bdc-4da0-883d-5a73a7c553ff@intel.com>
Date: Thu, 16 Jan 2025 08:44:36 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Fedor Pchelkin <pchelkin@...ras.ru>, Jon Mason <jdmason@...zu.us>
Cc: Allen Hubbe <allenbh@...il.com>, Logan Gunthorpe <logang@...tatee.com>,
 ntb@...ts.linux.dev, linux-kernel@...r.kernel.org,
 lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] ntb: use 64-bit arithmetic for the MSI doorbell mask



On 1/15/25 11:28 AM, Fedor Pchelkin wrote:
> msi_db_mask is of type 'u64', still the standard 'int' arithmetic is
> performed to compute its value.
> 
> While most of the ntb_hw drivers actually don't utilize the higher 32
> bits of the doorbell mask now, this may be the case for Switchtec - see
> switchtec_ntb_init_db().
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE static
> analysis tool.
> 
> Fixes: 2b0569b3b7e6 ("NTB: Add MSI interrupt support to ntb_transport")
> Cc: stable@...r.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>

LGTM. Should be using the BIT() macro to begin with. 

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
>  drivers/ntb/ntb_transport.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index a22ea4a4b202..4f775c3e218f 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -1353,7 +1353,7 @@ static int ntb_transport_probe(struct ntb_client *self, struct ntb_dev *ndev)
>  	qp_count = ilog2(qp_bitmap);
>  	if (nt->use_msi) {
>  		qp_count -= 1;
> -		nt->msi_db_mask = 1 << qp_count;
> +		nt->msi_db_mask = BIT_ULL(qp_count);
>  		ntb_db_clear_mask(ndev, nt->msi_db_mask);
>  	}
>